The present invention relates to industrial control systems providing motion control and in particular to a system of generating electronic cams used for programming motion control.
Mechanical cams may convert a rotary motion to a periodic linear motion, for example, through the use of a cam wheel having an irregular radius and attached to a rotating shaft. A follower riding along the perimeter of the cam wheel moves in and out according to the angle of the shaft and the radius of the cam wheel currently in contact with the follower.
Modern industrial control systems may implement cam motion by abstracting the cam as a set of points of a cam function or cam equation. The desired linear motion may then be implemented by an alternative technology such as a servo actuator without the need for a mechanical cam. By creating a virtual cam, the benefits of cam type motion are in the form of predetermined and well-defined velocities, acceleration, and jerk (the derivative of acceleration) and these characteristic may be easily modified via software modifications.
A variety of tools exist for the generation of virtual cam profiles for new designs. Normally the profiles from these tools are captured as a set of points in a cam profile table, for example, linking shaft rotation values with given linear motion values. These complex tools are very specific and are not flexible enough to meet the needs of all designs. Therefore most designers have additional tools and proprietary profiles that provide the ability to meet the needs of their design. Thus developing a successful cam profile can be extremely complex requiring expert assistance.
A common requirement in cam design is to replicate and modify a portion of an existing profile, when the original designer is not available, and the only information still in existence are a set of points used to define the input to output translation. As part of the replication it is often required to modify portions of the profile (such as distances or ratios) while maintaining the same behavior, i.e. maintaining the boundary conditions. Unfortunately, conventional tools and algorithms used to modify the design are incomplete and will often distort the original profile. Thus additional mathematical information used during the creation of the original profile needs to be available, in the form of re-engineering, reverse engineering or manual segmentation (splitting the profile into many segments in an attempt to control the overall profile). The result of this process is typically limiting (not all parts of all segments can be scaled within the given boundaries) or expensive (it takes significant time to regenerate the original design).